Events Calendar

Astani Civil and Environmental Engineering Seminar

Speaker: Shengli Chen, integrated PoroMechanics Institute, the University of Oklahoma

Talk Title: Poroelastoplastic analytical solution of a cylindrical cavity in saturated rock formation

Abstract: The cavity expansion/contraction theory has wide applications in the areas of in-situ testing such as pressuremeter and piezocone penetrations, underground excavations and tunnel constructions in soil and rock, and wellbore instability in the oil and gas industry. In this research, a class of exact analytical solutions have been developed for the tunnel excavation/wellbore drilling problems in elastoplastic rock masses subjected to non-isotropic initial stresses, using the cavity contraction method and under both drained and undrained conditions. To provide realistic predictions of the rock behaviour, especially for the shale formation, the critical state-based modified Cam Clay and bounding surface models were adopted in the analyses. The uniqueness and novelty of the proposed analytical approach lies in the fact that the cavity boundary value problem is formulated within the Lagrangian description according to which both the constitutive relations and the equilibrium equation are described in terms of individual material particle. It is therefore possible to capture the evolution of the stress components and pore pressure/void ratio for any material point throughout the tunnel excavation/wellbore drilling processes, from elastic phase to elastoplastic and even failure phases of the deformation.
Numerical simulations were also conducted with the use of ABAQUS software. A user defined material subroutine (UMAT) has been developed and implemented into ABAQUS for the bounding surface model (Dafalias & Herrmann, 1980). The predictions from the ABAQUS analyses are generally in excellent agreement with the analytical solutions developed for both modified Cam Clay and the bounding surface models. The results show clearly that the stress history (overconsolidation ratio) has significant influence on the stress and pore pressure distributions as well as the development and progress of the plastic/elastic zones around the cavity.


Host: Astani CEE

Location: Kaprielian Hall (KAP) - 209

Audiences: Everyone Is Invited

Contact: Cassie Cremeans